EP2647688A1 - Method for loosening deposits containing alkaline earth metal sulphates - Google Patents

Abstract

Dissolving alkaline earth metal sulfates having deposits in subterranean plants or plant components, comprises passing an aqueous formulation into underground plants to release the deposits, and allowing to interact with the deposits, where the aqueous formulation comprises at least (i) 15-98.98 wt.% water, (ii) 1-75 wt.% methanesulfonic acid, (iii) 0.01-5 wt.% at least one water-miscible organic solvent, and (iv) 0.01-5 wt.% at least one corrosion inhibitor, and the pH value of the formulation is = 2.5 and the sum of components (i)-(iv) is at least 80 wt.% based on the sum of all components.

Description

The present invention relates to a process for dissolving deposits containing alkaline earth metal sulphates in underground facilities or plant components for the production of crude oil, natural gas and / or water by treating the deposits with an aqueous formulation containing methanesulfonic acid.

In the course of oil and / or natural gas production, solid deposits of inorganic or organic substances may form in the petroleum formation itself, in underground parts of the facility, such as the borehole lined with metal pipes, as well as in above-ground plant components such as separators. The formation of such deposits is highly undesirable because they at least hinder the extraction of oil and can lead in extreme cases to a complete blockage of the affected parts of the plant.

In the course of oil or natural gas production is usually not only oil and / or natural gas promoted, but also more or less saline water. It may be water contained in the formation or condensed water, or water that has been injected into the subterranean formation via an injection well to maintain pressure. Saline water can also be used in geothermal energy production, in which one promotes hydrothermal water, are promoted, in which injected through an injection well cold water into a rock formation and removes warm water through a well.

Deposits of poorly soluble inorganic salts such as deposits of calcium carbonate or calcium, strontium or barium sulfate can form, because in the rock formation under the naturally given conditions (high pressure, high temperature), a higher concentration of salts can be dissolved in the formation water than under normal conditions (1 bar, room temperature). If formation water saturated with inorganic salts reaches zones of low temperature and / or lower pressure on the way to the earth's surface, poorly soluble salts may precipitate, e.g. still in the formation itself, on the inner surface of the metallic lining of the production well or only in aboveground plant parts such as pipelines or separators. Furthermore, deposits can be formed by intermixing incompatible waters, such as injected water and formation water, thereby precipitating solids.

Above-ground plant components are relatively easily accessible, and can in principle be mechanically cleaned. Therefore, the cleaning of such equipment parts generally presents no difficulties.

The cleaning of contaminants in underground plant parts, in particular in the borehole itself or in reservoir rock causes greater difficulties.

While carbonaceous deposits in the wellbore or reservoir rock can be relatively easily dissolved using acids such as HCl, removal of sulfate-resistant deposits, particularly calcium, strontium, and barium sulphates, poses major problems because they are sparingly soluble in HCl.

Thus, devices are known which can be introduced into the borehole and can detect and remove deposits, for example using ultrasonic techniques such as US 6,886,406 disclosed. However, such techniques are comparatively expensive.

Furthermore, it is known to solve impurities in the borehole using certain formulations.

US 2,877,848 discloses the use of complexing agent EDTA or salts thereof for dissolving deposits such as BaSO ₄ in the wellbore. Optionally, nonionic surfactants can be added to the formulation.

US 4,980,077 discloses a method for solubilizing deposits of alkaline earth metal sulfates with polyaminocarboxylates as complexing agents in a concentration of 0.1 to 1 mol / l at a pH of 8 to 14. The complexing agent may be EDTA or DTPA. The formulation further comprises oxalate ions in a concentration of 0.1 to 1 mol / l.

US 5,282,995 discloses a method for solubilizing alkaline earth metal sulfate deposits with polyaminocarboxylates such as EDTA or DTPA in alkaline medium. The formulation further comprises formate ions.

US 5,548,860 discloses a method for solubilizing alkaline earth metal sulfate deposits with polyaminocarboxylates such as EDTA or DTPA in alkaline medium. The formulation further comprises a synergist selected from the group of oxalate, thiosulfate, salicylate or nitriloacetate anions. The detachment is supported by ultrasound.

However, the use of alkaline solutions of complexing agents such as EDTA or DTPA has a number of disadvantages.

Alkaline earth metal ions such as Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and / or Ba ²⁺ and HCO ₃ -containing deposit water has a low pH. By injecting an alkaline solution of complexing agents into a wellbore, at least a portion of the alkaline solution mixes with the reservoir water. This leads to secondary precipitates, for example of Mg (OH) ₂ , Ca (OH) ₂ or CaCO ₃ , which can clog the formation and / or the borehole. Furthermore, the efficiency is low: the complexing agent initially complexes the alkaline earth metal ions present in the solution and initially does not attack the deposits.

Therefore, measures must be taken to prevent the reservoir water and the alkaline solution of the complexing agent from mixing with each other. For this purpose, for example, it is possible to rinse the borehole in a preceding step with a rinsing liquid and / or to shut off the borehole so that no reservoir water can penetrate into the borehole any more. This can be done, for example, mechanically by means of an insert which closes the perforations of the borehole lining. Such measures naturally mean additional expense.

WO 2006/092438 A1 discloses the use of water-soluble alkanesulfonic acids to increase the permeability of subterranean, carbonaceous petroleum or natural gas bearing rock formations and to dissolve carbonaceous and / or carbonate-bearing contaminants in petroleum production. The dissolution of sulphate-containing deposits is not described.

The older registration US 61/475531 discloses a method of dissolving deposits of surfaces with an aqueous formulation comprising 3 to 15 wt.% of at least one complexing agent selected from the group of MGDA, NTA, HEDTA, GLDA, EDTA or DTPA and 3 to 15 wt.% of at least one acid. The acid may be, for example, methanesulfonic acid. The pH of the formulation is 3 to 9. The deposits may be, for example, CaCO ₃ or CaSO ₄ . The surfaces to be debris-free may be, for example, the surfaces of turbines, ship hulls, solar panels, osmotic membranes, heating elements, reactors, oil wells, water wells, geothermal wells, or oil wells.

The object of the invention was to provide an improved process for the removal of deposits of alkaline earth metal sulfates in underground facilities or facilities for the production of oil, natural gas or water to provide, which does not have the disadvantage of causing secondary deposits.

(I)

15 Gew. % bis 98,98 Gew.-% Wasser,

(II)

1 Gew. % bis 75 Gew.-% Methansulfonsäure,

(III)

0,01 Gew. % bis 5 Gew.-% mindestens mit Wasser mischbaren organischen Lösemittels sowie

(IV)

0,01 Gew. % bis 5 Gew.-% mindestens eines Korrosionsinhibitors umfasst,

und wobei der pH-Wert der eingesetzten Formulierung ≤ 2,5 ist und die Summe der Komponenten (I), (II), (III) und (IV) mindestens 80 Gew. % bezüglich der Summe aller Bestandteile beträgt.Method for dissolving deposits containing alkaline earth metal sulphates in underground installations or installations for conveying oil and / or natural gas and / or water from subterranean formations by depressing an aqueous formulation for dissolving the deposits in the underground installations and allowing them to act on the deposits, wherein the aqueous formulation is at least

(I)

From 15% to 98.98% by weight of water,

(II)

From 1% to 75% by weight of methanesulfonic acid,

(III)

0.01 wt.% To 5 wt .-% of at least water-miscible organic solvent and

(IV)

0.01% by weight to 5% by weight of at least one corrosion inhibitor,

and wherein the pH of the formulation used is ≤ 2.5 and the sum of components (I), (II), (III) and (IV) is at least 80% by weight relative to the sum of all components.

In a preferred embodiment of the method, the underground installations are a borehole or the reservoir rock, particularly preferably the borehole.

In a likewise preferred embodiment of the method, the subterranean formation comprises formation waters with ions dissolved therein selected from the group of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ , and the plant components are available during the execution of the method Contact with the formation water.

More specifically, the following is to be accomplished for the invention:

To carry out the process according to the invention, an aqueous formulation is used which comprises at least the components (I), (II), (III) and (IV). In addition to components (I) to (IV), the formulation used may optionally comprise further components.

As component (I), the formulation comprises water.

As component (II), the formulation comprises methanesulfonic acid. Methanesulfonic acid is commercially available, for example in pure form or as an approximately 70 wt .-% aqueous solution.

As component (III) it comprises at least one water-miscible organic solvent. The deposits to be dissolved in the plants or plant components are usually wetted with oil, which hinders rapid dissolution of the deposits. Organic solvents therefore allow faster separation. The solvents used may be wholly or only partially miscible with water. The minimum requirement is that no phase separation of water and organic solvents occurs at the concentration used and under the conditions of use.

Examples of suitable organic solvents include alcohols such as ethanol, n-propanol, i-propanol, n-butanol, i-butanol, glycols such as ethylene glycol, diethylene glycol, propylene glycol or glycol ethers such as ethylene glycol monobutyl ether. Of course, mixtures of several different water-miscible, organic solvents can be used.

As component (IV), the formulation comprises at least one corrosion inhibitor. Examples of suitable corrosion inhibitors include polyether phosphates, butynediol, butynediol alkoxylates or alkyl phosphates. Of course, mixtures of several different corrosion inhibitors can be used.

According to the invention, the pH of the formulation used is ≦ 2.5, preferably ≦ 2, and particularly preferably ≦ 1. The pH can be easily adjusted by the person skilled in the art in a manner known in principle by the concentration of methanesulfonic acid.

Examples of further optional components of the formulations include further acids in addition to the methanesulfonic acid, such as hydrochloric acid, hydrofluoric acid, formic acid or acetic acid or surfactants. Complexing agents can be present in small amounts in special cases as further components, but are preferably not present.

According to the invention, the formulation comprises the components (I) to (IV) in the following amounts (all data in% by weight): (I) water 15 - 98.98 (II) Methanesulfonic acid 1 - 75 (III) Organic solvents 0.01 - 5 (IV) corrosion inhibitors 0.01 - 5

The following amounts can preferably be used (all data in% by weight): prefers particularly preferred very particularly preferred (I) water 44 - 94,8 56 - 89.6 66 - 83.6 (II) Methanesulfonic acid 5 - 50 10 - 40 16 - 30 (III) Organic solvents 0.1 - 3 0,2 - 2 0,2 - 2 (IV) corrosion inhibitors 0.1 - 3 0,2 - 2 0,2 - 2

According to the invention, the sum of components (I), (II), (III) and (IV) is at least 80% by weight with respect to the sum of all constituents, preferably at least 90% by weight, more preferably at least 95% by weight and most preferably 100% by weight, ie, apart from components (I) to (IV), no further components are present in the formulation. If further components are present at all, their amount should furthermore generally not exceed 50% by weight, preferably 25% by weight and more preferably 10% by weight, of the amount of components (II), (III) and (IV).

In the process according to the invention, the formulation is used for dissolving deposits containing alkaline earth metal sulfates in underground installations or plant components for the extraction of crude oil and / or natural gas and / or water from subterranean formations.

The subterranean formations may be subterranean oil and / or natural gas deposits, the petroleum or gas deposits comprising, in addition to petroleum and / or natural gas, more or less saline formation water. The reservoir water may be of natural origin, or it may also be water injected into the formation. For injecting into formations freshwater or saltwater can be used. Saltwater, for example, may be seawater, or may be treated reservoir water that is re-injected.

The formation water may in particular be alkali metal ions and alkaline earth metal ions and, as anions, halide ions, in particular chloride ions, as well as other ions such as sulfate ions. In particular, it is formation water which comprises dissolved alkaline earth metal ions, in particular those selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ and furthermore dissolved SO ₄ ^2- .

Furthermore, it may also be formations from which only water is promoted. The water may be natural water in the formation, or water that has been injected into the formation, for example, for geothermal energy.

The subterranean plant parts are such subterranean plant parts which hydraulically connect the subterranean formation with the earth surface, i. plants or plant components which ensure a flow path for crude oil, natural gas and water from the formation to the earth's surface. In particular, these are boreholes including conventional wells, such as the borehole wall of steel pipes, production lines, tail-pipes and their equipment or pump elements such as rotors, stators or pump rods. It may also be reservoir rock, in particular the reservoir rock surrounding the borehole. Particularly preferred are boreholes, in particular boreholes lined with steel pipes.

The deposits can be deposits containing all types of alkaline earth metal sulphates. Examples include CaSO ₄ , CaSO ₄ .½H ₂ O, CaSO ₄ .2H ₂ O, SrSO ₄ or BaSO ₄ .

In addition to the alkaline earth metal sulfates, the deposits may contain other components. To mention here are on the one hand carbonatic deposits, such as CaCO ₃ and / or MgCO ₃ deposits. On the other hand, the deposits can be contaminated with oils and / or oil components such as paraffins, asphaltenes or napthenates or with residues of corrosion inhibitors.

The deposits can be located on the inner walls of the plants or plant parts, for example on the inner wall of boreholes. However, for example, they may also have added holes in whole or in part, for example the perforation of the borehole at the hydraulic connection to the formation. Deposits may also be within the formation near the wellbore. Such deposits prevent the transport of hydrocarbons to the wellbore.

The erfindungemäße method is exercised by pressing the above-described formulation in the underground facilities or plant components, in particular in the well and optionally in the reservoir rock and act on the deposits. This can be done by conventional pumps, and the pressure is chosen by the skilled person depending on the circumstances. By means of the pressure, the person skilled in the art can influence how far the formulation can penetrate into the plants or system components or, if appropriate, through the perforation into the formation.

The deposits comprising alkaline earth metal sulfates dissolve under the influence of the aqueous, methanesulfonic acid-containing formulation. The exposure time is determined by the skilled person depending on the desired result. It may in particular be 1 h to 300 h, preferably 2 h to 200 h, without the invention being restricted to this duration. It is conceivable to preheat the formulation to a certain temperature. Typically, the formulation in the plant or parts of the plant will, over time, heat up to the temperature prevailing in these plants or plant components, the temperature usually not being uniform, but being variable, for example, depending on the depth of the borehole.

In a preferred embodiment of the invention, the subterranean formation comprises formation water with ions dissolved therein selected from the group of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ , the plant parts being in contact with each other during the execution of the process stand the formation water.

In one embodiment of the invention, the plant or the plant part, for example a borehole, may still contain residues of the ion selected from the group consisting of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ^{2+-containing} formation water. It is the particular advantage of this invention that prior rinsing of the plant or parts of the plant prior to bringing into contact with the formulation to be used according to the invention is not necessary because the acid methanesulfonic acid formulation does not lead to precipitation with said ions.

Furthermore, during the execution of the method, the plant or the plant part can still be hydraulically connected to the formation so that formation water can still flow into the plant or the plant part and mix with the acidic formulation. It is not necessary to completely shut off the plant or the plant part hydraulically against the formation.

In a particularly preferred embodiment of the invention, in the treatment of a wellbore, the wellbore is not terminated with respect to the formation, but the connection to the formation, for example via a perforation in the borehole wall, remains open. In this embodiment, it is advantageous to flow formation water comprising ions selected from the group of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ into the well at least partially by applying a pressure equal to or greater than the pressure of the formation water. At approximately the same pressure, however, there will nevertheless be some mixing of acidic formulation and formation water at the point of contact. At one pressure, the acidic formulation may flow into the formation where it may also mix with formation water. In contrast to alkaline formulations with complexing agents, however, this does not result in secondary precipitations which could clog the formation.

• In den Versuchen wurden die Fähigkeit von Salzsäure, Methansulfonsäure sowie eines Komplexbildner umfassenden kommerziellen Reinigers für Sulfatablagerungen untersucht.

The following examples are intended to explain the invention in more detail:

• In the experiments, the ability of hydrochloric acid, methanesulfonic acid as well as a complexing commercial detergent for sulfate deposits were investigated.

Used material:

(A)

Hydrochloric acid, 10% strength by weight solution in water

(B)

Methanesulfonic acid, 20% by weight solution in water

(C)

Commercial deposition solubilizer (SRW 85247 Baker Petrolite) contains 30 to 60% by weight of the complexing agent disodium ethanediol glycinate and 1 to 5% by weight NaOH in aqueous solution, diluted with water to 20% by weight detergent, pH 10

(D)

Commercial sediment solubilizer such as (C) diluted to 20% by weight with water and HCl, pH 5

Calcium sulphate powder (Afla Aesar) General test procedure:

Each 2 g of the calcium sulfate powder was mixed with 40 ml each of Solvents (A), (B), (C) and (D) in a Teflon-lined closed steel vessel at various temperatures and times of up to 168 hours (ie 1 week) stored. After the end of the experiment and cooling to room temperature, the Ca content in the solution was analyzed in each case. For this purpose, the mixture in the steel vessel EDTA was added to prevent dissolved Ca ²⁺ from precipitating and it was filtered off over a very fine filter (0.2 .mu.m filter). The filtrate was used for analysis. Tests were performed at room temperature, 60 ° C and 90 ° C.

The results are summarized in Tables 1, 2 and 3.

The results show that the solubilizer (C), which comprises complexing agent and NaOH (pH 10), has good dissolving power for calcium. However, acidifying such a solubilizer to pH 5 in order to avoid the problem of secondary precipitation (experiment (D)), this solubilizer shows only a very slight effect.

Hydrochloric acid and methanesulfonic acid have a similar effect, but the methanesulfonic acid is known to be significantly less corrosive than methanesulfonic acid.

Claims (10)

Method for dissolving deposits containing alkaline earth metal sulphates in underground installations or installations for conveying oil and / or natural gas and / or water from subterranean formations by depressing an aqueous formulation for dissolving the deposits in the underground installations and allowing them to act on the deposits, characterized in that the aqueous formulation at least (I) 15% to 98.98% by weight of water, (II) 1% to 75% by weight of methanesulfonic acid, (III) 0.01 wt.% To 5 wt .-% of at least one water-miscible organic solvent, and (IV) 0.01 wt.% To 5 wt .-% of at least one corrosion inhibitor comprises, wherein the pH of the formulation used ≤ 2.5 and the sum of the components (I), (II), (III) and (IV) is at least 80% by weight of the sum of all components. A method according to claim 1, characterized in that the deposits comprise calcium, strontium and / or barium sulfate. A method according to claim 1, characterized in that it is deposits comprising strontium and / or barium sulfate deposits. A method according to any one of claims 1 to 3, characterized in that the subterranean formation comprises formation water with ions dissolved therein selected from the group of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ , and the plant parts during the Execution of the process in contact with the formation water stand. A method according to any one of claims 1 to 4, characterized in that the plant is a borehole and / or the adjacent reservoir rock. A method according to claim 5, characterized in that one does not shut off the borehole from the formation during the execution of the method. A method according to claim 6, characterized in that the inflow of formation water into the borehole is prevented by applying a pressure equal to or greater than the pressure of the formation water. A method according to any one of claims 1 to 7, characterized in that the aqueous formulation is at least (I) 44% to 94.8% by weight of water, (II) 5% to 50% by weight of methanesulfonic acid, (III) 0.1% by weight to 3% by weight of at least one water-miscible organic solvent and (IV) 0.01 wt.% To 3 wt .-% of at least one corrosion inhibitor. A method according to any one of claims 1 to 7, characterized in that the aqueous formulation is at least (I) 66 wt% to 83.6 wt% water, (II) 16% by weight to 30% by weight of methanesulfonic acid, (III) 0.2 wt .-% to 2 wt .-% of at least one water-miscible organic solvent, and (IV) from 0.2% to 2% by weight of at least one corrosion inhibitor. A process according to any one of claims 1 to 9, characterized in that the water-miscible organic solvent is at least one selected from the group of ethanol, n-propanol, i-propanol, n-butanol, i-butanol, glycols or glycol ethers.